EF6 code first

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.EF6

3.1初步目录及说明

下面是用VS2013开发环境创建的项目:

说明:控制台项目类型,安装EF版本为6.1.3, 数据库连接字符串配置:

  <connectionStrings>    <add name="DefaultConnection"         connectionString="Data Source=.;Initial Catalog=TestDB;UID=sa;PWD=123456"      providerName="System.Data.SqlClient" />  </connectionStrings>

EFContext.cs代码:

using Consoles.EF6.Models;using System.Data.Entity;namespace Consoles.EF6.Repositories{    public class EFContext : DbContext    {        public EFContext() : base("DefaultConnection") { }        public DbSet<Category> Categories { get; set; }        protected override void OnModelCreating(DbModelBuilder modelBuilder)        {            modelBuilder.Entity<Category>().HasKey(k => k.CategoryId) //设置主键                .Property(q => q.CategoryName).IsRequired();//设置不能为空        }    }}

注:

a.数据库上下文构造方法,继承基类,其参数是DefaultConnection,配置的数据库连接字符串中name值要一致;

如果name值和上下文类名(EFContext)一致的话,上下文类的构造方法也可以省略.

b.为了保持实体类"干净",不使用DataAnnotations数据注解特性,改为Fluent API配置方式.当然有些已经默认了,我们照样进行配置.

如:属性为Id(字母不分大小写)或为类名+Id,它会默认为主键,但我们也配置:Entity<Category>().HasKey(k => k.CategoryId)

疑问：这种两种方式，到底采用那种好呢？这个……我表示无语，你自个看那个爽啦。

3.2示例一

Category.cs代码：

namespace Consoles.EF6.Models{    public class Category    {        public int CategoryId { get; set; }        public string CategoryName { get; set; }        public string Description { get; set; }    }}

Program.cs代码：

using Consoles.EF6.Models;using Consoles.EF6.Repositories;using System;using System.Collections.Generic;using System.Linq;using System.Data.Entity.Migrations;namespace Consoles.EF6{    class Program    {        static void Main(string[] args)        {            #region 示例一            using (var db = new EFContext())            {                var categories = new List<Category>                {                    new Category(){ CategoryName="Mobile",Description="手机大类"},                    new Category(){ CategoryName="Computer",Description="电脑大类"}                };                //AddOrUpdate:根据指定列,相同就更新,不相同就添加                categories.ForEach(list => db.Categories.AddOrUpdate(c => c.CategoryId, list));                db.SaveChanges();                //var query = db.Categories;                 var query = from c in db.Categories select c;                //遍历输出                foreach (var item in query)                {                    Console.WriteLine("类别:{0};说明:{1}", item.CategoryName, item.Description);                }            }            #endregion            Console.ReadKey();        }    }}

运行结果：

查看数据库：

3.3示例二

我们添一个Subcategory.cs，其代码：

namespace Consoles.EF6.Models{    public class Subcategory    {        public int SubcategoryId { get; set; }        public string SubcategoryName { get; set; }        public int CategoryId { get; set; }        public Category Category { get; set; }    }}

再修改Category.cs代码：

using System.Collections.Generic;namespace Consoles.EF6.Models{    public class Category    {        public int CategoryId { get; set; }        public string CategoryName { get; set; }        public string Description { get; set; }        public ICollection<Subcategory> Subcategories { get; set; }    }}

设计关系为：大类Category：子类Subcategory=1：N。子类必须属于某一个大类，也就是外键不能为空。配置Fluent API

using Consoles.EF6.Models;using System.Data.Entity;namespace Consoles.EF6.Repositories{    public class EFContext : DbContext    {        public EFContext() : base("DefaultConnection") { }        public DbSet<Category> Categories { get; set; }        public DbSet<Subcategory> Subcategories { get; set; }        protected override void OnModelCreating(DbModelBuilder modelBuilder)        {            modelBuilder.Entity<Category>().HasMany(s => s.Subcategories)                .WithRequired(c => c.Category).HasForeignKey(f=>f.CategoryId);            modelBuilder.Entity<Category>().HasKey(k => k.CategoryId);            modelBuilder.Entity<Category>().Property(p => p.CategoryName).HasMaxLength(20);            modelBuilder.Entity<Subcategory>().HasKey(K => K.SubcategoryId);            modelBuilder.Entity<Subcategory>().Property(p => p.SubcategoryName).IsRequired();        }    }}

Program.cs代码：

using Consoles.EF6.Models;using Consoles.EF6.Repositories;using System;using System.Collections.Generic;using System.Linq;using System.Data.Entity.Migrations;namespace Consoles.EF6{    class Program    {        static void Main(string[] args)        {            #region 示例二            using (var db = new EFContext())            {                var categories = new List<Category>                {                    new Category(){ CategoryName="Mobile",Description="手机大类"},                    new Category(){ CategoryName="Computer",Description="电脑大类"}                };                categories.ForEach(list => db.Categories.AddOrUpdate(c => c.CategoryId, list));                db.SaveChanges();                var subcategories = new List<Subcategory>                {                    new Subcategory(){ SubcategoryName="2G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},                    new Subcategory(){ SubcategoryName="3G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},                    new Subcategory(){ SubcategoryName="4G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},                    new Subcategory(){ SubcategoryName="Desktop",Category=db.Categories.Single(c=>c.CategoryName=="Computer")},                    new Subcategory(){ SubcategoryName="Tablet ",Category=db.Categories.Single(c=>c.CategoryName=="Computer")}                        };                subcategories.ForEach(list => db.Subcategories.AddOrUpdate(c => c.SubcategoryId, list));                db.SaveChanges();                var query = from c in db.Categories select c;                foreach (var item in query)                {                    Console.WriteLine("类别:{0};说明:{1}", item.CategoryName, item.Description);                }            }            #endregion            Console.ReadKey();        }    }}

查看数据库：

嘎嘎！一对多关系OK!Subcategories表的外键也不为空！

3.4示例三

我们再添加一个Product.cs，其代码：

using System.Collections.Generic;namespace Consoles.EF6.Models{    public class Product    {        public int ProductId { get; set; }        public string ProductName { get; set; }        public ICollection<Subcategory> Subcategories { get; set; }    }}

再修改Subcategory.cs：

using System.Collections.Generic;namespace Consoles.EF6.Models{    public class Subcategory    {        public int SubcategoryId { get; set; }        public string SubcategoryName { get; set; }        public int CategoryId { get; set; }        public Category Category { get; set; }        public ICollection<Product> Products { get; set; }    }}

修改EFContext.cs:

using Consoles.EF6.Models;using System.Data.Entity;namespace Consoles.EF6.Repositories{    public class EFContext : DbContext    {        public EFContext() : base("DefaultConnection") { }        public DbSet<Category> Categories { get; set; }        public DbSet<Subcategory> Subcategories { get; set; }        public DbSet<Product> Products { get; set; }        protected override void OnModelCreating(DbModelBuilder modelBuilder)        {            modelBuilder.Entity<Category>().HasMany(s => s.Subcategories)                .WithRequired(c => c.Category).HasForeignKey(f => f.CategoryId);            modelBuilder.Entity<Category>().HasKey(k => k.CategoryId);            modelBuilder.Entity<Category>().Property(p => p.CategoryName).HasMaxLength(20);            modelBuilder.Entity<Subcategory>().HasKey(K => K.SubcategoryId);            modelBuilder.Entity<Subcategory>().Property(p => p.SubcategoryName).IsRequired();            modelBuilder.Entity<Product>().HasKey(k => k.ProductId);            modelBuilder.Entity<Product>().Property(p => p.ProductName).HasMaxLength(120);            modelBuilder.Entity<Subcategory>()             .HasMany(c => c.Products).WithMany(p => p.Subcategories)             .Map(t => t.MapLeftKey("SubCategoryId")             .MapRightKey("ProductId")             .ToTable("SubcategoryProduct"));        }    }}

查看数据库：

3.5初始化数据

前面我们是在Main方法写的模拟数据代码，是不是不太好？在“第05章”文中，我也说过有预留的问题，在这补充一下。

添加SampleData.cs，其代码：

using Consoles.EF6.Models;using System.Collections.Generic;using System.Data.Entity;using System.Linq;using System.Data.Entity.Migrations;namespace Consoles.EF6.Repositories{    public class SampleData : DropCreateDatabaseIfModelChanges<EFContext>    {        protected override void Seed(EFContext db)        {            var categories = new List<Category>                {                    new Category(){ CategoryName="Mobile",Description="手机大类"},                    new Category(){ CategoryName="Computer",Description="电脑大类"}                };            categories.ForEach(list => db.Categories.AddOrUpdate(c => c.CategoryId, list));            db.SaveChanges();            var subcategories = new List<Subcategory>                {                    new Subcategory(){ SubcategoryName="2G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},                    new Subcategory(){ SubcategoryName="3G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},                    new Subcategory(){ SubcategoryName="4G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},                    new Subcategory(){ SubcategoryName="Desktop",Category=db.Categories.Single(c=>c.CategoryName=="Computer")},                    new Subcategory(){ SubcategoryName="Tablet ",Category=db.Categories.Single(c=>c.CategoryName=="Computer")}                        };            subcategories.ForEach(list => db.Subcategories.AddOrUpdate(c => c.SubcategoryId, list));            db.SaveChanges();        }    }}

注:关于多对多关系的数据添加,参加"第05章"示例!

添加配置节点：

这样只要有访问数据库时，就会初始化数据了，如：

using Consoles.EF6.Models;using Consoles.EF6.Repositories;using System;using System.Collections.Generic;using System.Linq;using System.Data.Entity.Migrations;namespace Consoles.EF6{    class Program    {        static void Main(string[] args)        {            using (var db = new EFContext())            {                var query = from c in db.Categories select c;                foreach (var item in query)                {                    Console.WriteLine("类别:{0};说明:{1}", item.CategoryName, item.Description);                }            }            Console.ReadKey();        }    }}

我们并没在程序显式的代码中执行SampleData里的Seed方法,通过配置文件即可(在不需要时,也可以disableDatabaseInitialization关闭).

4.EF7

4.1目录及说明

下面是用VS2015开发环境创建的项目:

说明：ASP.NET 5版的WebApi项目类型；

依赖和Commands配置：

commands之ef是迁移用的，这在“第06章”已经介绍过，这里会略过。

4.2示例

由于EF7暂时不直接支持多对多实体关系（也可能我了解有限），所以这里举例一对多。

Category.cs代码：

using System.Collections.Generic;namespace WebApies.EF7.Models{    public class Category    {        public int CategoryId { get; set; }        public string CategoryName { get; set; }        public string Description { get; set; }        public ICollection<Subcategory> Subcategories { get; set; }    }}

Subcategory.cs代码：

namespace WebApies.EF7.Models{    public class Subcategory    {        public int SubcategoryId { get; set; }        public string SubcategoryName { get; set; }        public int CategoryId { get; set; }        public Category Category { get; set; }    }}

EFContext.cs代码：

using Microsoft.Data.Entity;using WebApies.EF7.Models;using Microsoft.Data.Entity.Metadata;namespace WebApies.EF7.Repositories{    public class EFContext : DbContext    {        public DbSet<Category> Categories { get; set; }        public DbSet<Subcategory> Subcategories { get; set; }        protected override void OnConfiguring(DbContextOptions options)        {            options.UseSqlServer(                "Server=(localdb)\\mssqllocaldb;Database=TestDB;Trusted_Connection=True;MultipleActiveResultSets=true");        }        protected override void OnModelCreating(ModelBuilder modelBuilder)        {            modelBuilder.Entity<Category>().HasMany(C => C.Subcategories).WithOne().ForeignKey(f=>f.CategoryId);            modelBuilder.Entity<Category>().Key(k => k.CategoryId);            modelBuilder.Entity<Category>().Property(p => p.CategoryName).MaxLength(20);            modelBuilder.Entity<Subcategory>().Key(K => K.SubcategoryId);            modelBuilder.Entity<Subcategory>().Property(p => p.SubcategoryName).Required();        }    }}

迁移完毕后，查看数据库：

注：MaxLength没有起作用！（完整版的sqlserver是正常的）

基架模板代码创建：

此时目录：

这是T4模板代码，这个MVC版的，webapi版本的还得等等了!

5.小结

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